The present invention relates to an image forming apparatus such as electrophotographic copying machines, printers and facsimiles, and to an image forming unit used for the image forming apparatus.
One of conventional image forming units is provided with a rotatable photoconductor and a charging roller which has a shaft to contact with the outer face of the photoconductor (see JP 63-149669 A). This charging roller is put into pressure contact with the photoconductor by e.g. a spring which presses the shaft toward the photoconductor, so that the charging roller rotates following the rotation of the photoconductor. The charging roller applies electric charge to the photoconductor.
Another conventional image forming unit applies electric charge to a photoconductor by bringing a charging sheet into contact with the photoconductor (see JP 07-191523 A).
However, cost has increased in the case of the firstly-stated conventional image forming unit where the charging roller is provided with the shaft. Also, the structure becomes complicated because members such as springs are required so as to bring the charging roller in pressure contact with the photoconductor.
In the case of the secondly-stated conventional image forming unit where the charging sheet is brought into contact with the photoconductor, there has been a problem that image noises are generated by abnormal electric discharges due to deposits. The deposits are adhering substances accumulated on the contact portion between the charging sheet and the photoconductor. Specifically, they are toners, post-processing agents for toners, paper powders and the like which have passed through a cleaning blade.